Roller pumps are known to the prior art and have wide application in the medical field. A typical application for such a pump is as a blood pump during hemodialysis, for example. Other applications are well known. The simplicity and reliability of roller pumps has resulted in their wide acceptance within the medical community.
Typically, medical roller pumps employ a stator having a bearing surface against which one or more hoses is compressed by a rotating rotor, the rotor engaging the hoses with two or more rollers. On rotation of the rotor, the fluid medium in the hose or hoses is transported in the direction of the rotor rotation. Alternatively, the fluid may be presented to the pump under pressure such that rotation of the rotor causes the pump to serve as a measuring valve. In either instance, knowledge of the inner diameter of the hose or hoses and the rotational speed of the rotor provides a knowledge of the amount of fluid passed through the hose or hoses, which amount can be regulated by regulating the speed of the rotor.
Among the problems encountered in prior art roller pumps are dimensional variations in the rotor rollers as well as variations in the stator bearing surface and the hoses themselves. In addition, the rotor rollers have not always rolled over the hoses but, instead, have a tendency to "scuff" the hoses. Hose flutter is also known. Each of these phenomena, if prolonged, may result in mechanical failure of the hoses. Also, because the hose is not compressed against the stator bearing surface throughout the full 360.degree. rotation of the rotor, the forces imparted to the rotor are not uniform throughout its rotation. In larger pumps, this can be countered by increases in the size of the driving shaft. However, in smaller units, this solution may not be practical. In all cases, this results in significant variations in the torque required to rotate the rotor through 360.degree..